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The trio of BSS-601 model spacecraft will replace
an aging constellation and serve as the primary means of continuous, high-data-rate
communication with the Space Shuttle, with the International Space Station, and with
dozens of unmanned scientific satellites in low-Earth orbit. The new satellites will
augment the system's existing S- and Ku-band frequencies by adding Ka-band capability. To
support this increased capacity, the contract included the upgrade of the two TDRS
stations at White Sands, N.M.

The first satellite, TDRS-H, was successfully launched on 30 June 2000. The second
satellite, TDRS-I, was successfully launched on 8 March 2002. NASA is supplying three
launch vehicles for TDRS replenishment. The satellites will be placed in geosynchronous
orbit in strategic positions above the Pacific and Atlantic oceans.

The body-stabilized BSS-601 model on which the new
TDRS satellites are based was introduced in 1987 to perform missions demanding flexibility
and high power. The series has proved extremely popular and reliable, with more than 84
purchased by customers around the world.

A unique feature that contributed to Boeing's selection is TDRS' innovative springback
antenna design. A pair of 15-foot-diameter, flexible mesh antenna reflectors fold up for
launch, then spring back into their original cupped circular shape on orbit. These
steerable, single-access antennas can simultaneously transmit and receive at S-band and
either Ku- or Ka-band, supporting dual independent two-way communication. The selection of
Ku- or Ka-band communications is done on the ground. Receive data rates are 300
megabits/second at Ku- and Ka-band, and 6 Mbps at S-band. The spacecraft carries
additional capability for Ka-band receive rates of up to 800 Mbps. Transmit data rates are
25 Mbps for Ku- and Ka-band, and 300 kilobits/second for S-band.

In addition, an S-band phased array antenna can receive signals from five spacecraft at
once, while transmitting to one.

On-orbit power derives from two wings covered with silicon solar cells that generate
2,300 Watts. A nickel-hydrogen battery supplies payload power during eclipses.

TDRS 8 suffered problems with its multi-access antenna.

TDRS 9 lost pressure in one of its four onboard fuel tanks four days after launch.
Satellite controllers at BSS since then re-routed fuel tank pressurant around a blocked
valve and conducted a series of engine burns to raise TDRS-9's orbit to 35,800 km. The
last burn, which put the spacecraft in its final geosynchronous orbit, was performed on 30
September 2002.